The signal transmission device as described above is provided with: a plurality of communication modules equipped on a board on which a semiconductor chip (IC chip) is mounted; and a cooling mechanism for cooling these communication modules.
A heatsink is cited as an example of the cooling mechanism for the communication modules, and a conventional signal transmission device can be roughly classified as follows based on an aspect of the heatsink. That is, the conventional signal transmission device can be roughly classified into a type in which the heatsinks are provided respectively for the plurality of communication modules (see Japanese Patent Application Laid-Open Publication No. 2010-175995 (Patent Document 1)) and a type in which one heatsink is provided for the plurality of communication modules, and the latter is called “aggregation type” and is distinguished from the former. Accordingly, also in the following explanation, a type of a signal transmission device in which a common heatsink is provided for the plurality of communication modules is called “aggregation type” in some cases.
In the conventional aggregation-type signal transmission device, the heatsink is placed on the plurality of communication modules so as to cover these communication modules. Therefore, it is not required to widen a distance between the communication modules adjacent to each other in order to avoid interference between the heatsinks adjacent to each other, so that there is a merit that the plurality of communication modules can be highly densely arranged in periphery of the IC chip.